Being an all encompassing, all powerful evil entity, there was no way to combat him the present. So, you have to abort him before his ill will infects all of creation.... somewhere in a cave at the beginning of time. There are several methods of time travel, but the only one available to you at the moment had no guarantee that living beings could survive the trip. So... the character's spirits where transfered into robots, retaining their equipment and psychic powers, and off they went.

Enter the vagina... climb up the birth canal... and face off with a giant cervix with your face on it. In cues music in it's 8-bit glory that quickly transitions to metal. No, seriously... the song is metal. These guys agree. Well, after Pokey (Eric Cartman in a time traveling spider-mech) turns off the machine that was maintaining the boss's subdued true form, out flows the swirling menstral fluid face of death. As fight the fight goes on Giygas spews incomprehensible nonsense that was inspired by a rape scene from a movie that scarred Itoi (series creator) when he was a child, and one of the bosses last forms takes the shape of a fetus heads.

Note: Giegue is Giygas. Nintendo is just inconsistent in their translations (for example, in Brawl Pokey is now "Porky" ((his original name). The true translation of his name is Giyig, but this was never used... so the link between the characters is often debated... though in Japan, it's pretty clear. Giyig was the final boss in Mother.. and Mother 2 had the title "Giyig strikes back". I would also like to point out that Giygas's original design in Mother is what inspired Mew and Mewtwo... although "inspired" might be stretching a bit. The developers of the first two games of the series was Ape Inc.... which was later renamed Creatures Inc... of Pokemon fame. One of the two lead composers of the Mother series is the current president of the company.

The original Giygas in Mother (final fight)

Mother: Early 1900s: Aliens abduct a young couple, George and Maria, to study humans in hopes of making peaceful contact. Giygas was born around this time, and in good faith, they decide to let this couple raise him. They loved him, and memories of his childhood proved to be his only weakness, though singing in general seemed to have always cause him pain, as Maria recalled.

"I loved him as if he was my own child. He was always wagging his tail just like a pup... EXCEPT for when I tried singing lullabies to him"

Mother: Early 1900s: Sometime later: George has been secretly studying the aliens in return... and he somehow picked up on their psychic abilities. After this was revealed... the alien race felt betrayed, and decided that humans now posed a threat. At some point Maria trapped herself inside her own magicant (a dream like world created by one's own mind... one that can be used as a means to imprison/ banish someone), while George stayed on earth raising what was left of his family, and spreading his research of PK (Psycho Kinetic) abilities. Giygas felt especially betrayed by this, and this fueled his campaign to rise to the top of the ranks of his society... eventually becoming his race's leader.

Mother: 1980s The invasion begins. Ninten, the great grandson of George and Maria, sets off on a journey to save the world. They eventually encounter Giygas and bring him down by singing the lullaby Maria wrote for him.

The game ends here, but not before a cliffhanger of a man on the phone telling you that the war wasn't over yet.

Mother (As explained by buzz buzz in Mother 2): 1990s: Giygas returns to in a plot that parallels what happened in Mother 2, only he succeeded in his invasion this time and his race set off to conquer the rest of the universe.

Mother: 2000s (semi-theory, as a few bits are unclear in the games): At some point Buzz Buzz's people defeated Giygas by trapping him in his own magicant and banishing him to the beginning of time... leaving him in his most vulnerable state.

This is where the time line changes. Giygas no longer invades in 1980 and again in 1990 with the rest of his race.

Mother 2: Beginning of time: Giygas eventually frees himself from his own magicant by using his immense power to shed his mind and body

Mother 2: 1990s: The damage done by Giygas in the original timeline in the 2000s was too severe to salvage, so Buzz Buzz's people send him ten years into the past in the body of a bee to warn Ness about the events to come... though his story was cut short by Pokey's mother swatting at him thinking he was a fly (not really a spoiler as this happens at the begining of Mother 2). Giygas attempts to invade the earth again, only this time in a different manner. In Mother he did it by using science and technology using his mothership as a base of operations. In Mother 2, there is no alien race. Giygas is alone in his work... and he does it by "infecting" the world with his presence... since he can no longer directly influence the world in his current state (being nothing more than his former self's subconscious). Though... the technology used in the first (like the Starmen for example) remains. There is no way to defeat him because he is everywhere and nowhere. The invasion was a long time in the making, and the only way to stop it is to prevent it from happening. The only option is to travel back to the beginning of time... which is what the heroes of Mother 2 set off to do.

Your mother and brother are both killed by a "family friend" in the first act of the game, your father going insane and taking it out on the townspeople soon after.

(insert the rest of Mother 3)

Your Brother eventuallyreturns as luke skywalker (he is wearing an x-wing-suit and has a light sabre) and tries to kill you repeatedly... killing off your team mates in a single hit when you last face him.... the only thing protecting you from his powerful lightning attacks being the badge imbued with the ghost of Benjamin Franklin... the Franklin Badge! Why do you fight him? Because he is now Pokey's right hand man.

In Mother 3, Pokey becomes evil. Not just a prankster who's cowardice drives him to the protection of people stronger than himself (first a cult leader, then a mafia boss who was running the city of Fourside.... and eventually the ultimate evil Giygas)... but a truly sadistic piece of shit. In his time machine he has been traveling through a countless number of time periods and fucking up history wherever he could for what he tells us has been somewhere between 1,000 to10,000 years worth of time (he stopped counting). He was immensely bored of life. After witnessing the destruction of society once before, he decides he wanted to witness a true armageddon of his own doing. In the first destruction, a small group of humans had left the earth while the rest of the population was killed off. They eventually return and create a new way of life in what we now know is nowhere island, and Pokey helps them along the way... enlisting the help of people he kidnapped from other time periods, including the creator of the human time machine Dr Andronuts. He eventually creates a booming metropolis in his own image (ie stupid and childish)... but his influence doesn't end there. After creating gross hybrids of all the remaining animal life... he decides enough was enough. The only thing he could get kicks from at this point on was seeing the destruction of human kind one last time... so he sets off to destroy the world. He knows he will be alone after this point (he was somehow banished from time travel from a higher power) but he takes solice in the fact that he would be the one that was responsible for it. Being his last "prank", he was glad he was going out with a bang.

After Lucas defeats his brother Claus, Lucas decides to pull the final pin anyways (the method in which Pokey was trying to destroy the world) and we see the destruction ourselves... in hopes that life can start anew without Pokey's influence.

(We don't see this happen, but after the games credits we see dialogue of all the characters talking to each other about how frightening it was, giving us the impression that they all survived and all is now going well. At the very least, better than it was.)